


Bad Behavior

by GoodValhalla



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - Canon Divergence, Alternate Universe - Vampire, Blood, Blood Drinking, F/F, Fluff, Vampire/Vampire Relationship, Vampires, vampire!Byleth, vampire!edelgard
Language: English
Status: In-Progress
Published: 2020-03-01
Updated: 2020-03-14
Packaged: 2021-02-28 10:07:28
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 2
Words: 2,336
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22968223
Author URL: https://archiveofourown.org/users/GoodValhalla/pseuds/GoodValhalla
Summary: Vampire AU.Edelgard and Byleth are both vampires. One is the Emperor, the other is not. One searches for the other, the other does not want to be found.What happens when they meet again?
Relationships: Edelgard von Hresvelg & My Unit | Byleth, Edelgard von Hresvelg/My Unit | Byleth
Comments: 14
Kudos: 88





	1. Chapter 1

Edelgard sat idly on her throne, waiting for her court to go through the motion. It was a bright sunny day, and all the velvety curtains in the throne room were drawn.

The lords and advisors offered their share of complaints and compliments, but they all sounded the same after all these years. 

She inherited the throne too young, some may say. Only a few knew it was going to be another matter: she would stay on the throne for too long. 

The bards sang her praises, sang about her youthful appearance, wished her eternal and just. Long live the Emperor! 

The people who loved her did not know how literally it was going to be.

One reported a series of murders at the other end of her land. Victims left drained of blood. It was concerning, certainly. Not surprising.

Her mind drifted. It has been five years since the war, ten years since she inherited the throne. It felt way longer than that. She was either bored out of her mind or worked to death. She had no idea how she was going to spend her newfound immortal days, if every day was the same as this one.

She noticed Hubert wearing the expression when he had something to report. Something important, probably. Because only she could tell his emotionless face was ten percent different from the usual. 

She dismissed the assembly to hear what he had to say. 

Later, in the Emperor’s study, Hubert emerged from the shadow, delivering the news.

“More murder cases In the trading port,” he said. “Victims are all drained of blood, like the previous ones.” He paused briefly. “Do you think it’s her?”

“I don’t know what to think,” Edelgard admitted with a sigh. “What about the survivor?”

“Still recovering. The chance is slim.”

“Did he say anything about his attacker?”

“He briefly regained consciousness, yesterday,” Hubert said. “Said it was a woman, though in more vulgar terms.”

“I see.”

“If it’s any condolence, the victims are usually convicts and bandits. I’m sorry, Lady Edelgard.”

What was he sorry about? That their beloved mentor had become a cold-blooded murderer, leaving a trail of bodies along the coastal towns? The infamous killer has gained the reputation of an "Ashen Demon". If Edelgard had anything to say, she certainly knew who this demon was.

“Send the most elite forces after her. Or, put a bounty on her head. I don't care how, bring her to me. Alive,” Edelgard said. “I will be taking dinner in my chamber.”

“Of course, Lady Edelgard.” Hubert bowed slightly.

Did she still want to find her, even though they were both monsters? One worse than the other. Even so, Edelgard was not proud of being the better one. She could not argue which was worse, taking blood from the loyal and willing servants every night, or hunting down not-so-innocent civilians for food.

Both options were pretty bad, considering they were both bloodsuckers.

Like a match made in heaven, they probably deserve each other.

***

It had been five years since the last battle of the war. Five years of peace—five years of a vampire on the throne. Edelgard had come to accept her unusual existence. Every time she felt nauseous about not being human, she reminded herself of the brighter side. She accepted the fact that if not for her mentor, she would not still be alive. 

At the end of the last battle, as she laid dying in a pool of her own blood, she thought she had seen galaxy itself. 

Drifting between consciousness and the abyss, her mind kept going back to one place: a chilly autumn night at the old monastery. Edelgard was walking through the corridor—if she must admit, because of insomnia—and found the professor wandering the halls like a ghost. 

It was a quiet moment, shrouded by soft moonlight through the windows. It was the moment that she realized her crush on her teacher was probably not as under control as she had previously thought. She prayed Byleth did not notice her out after curfew, or worse, her admiration borderlining on inappropriate behavior. 

Then snapped back to the chaos of the battlefield. It was loud, dirty, and filled with the disgusting stench of death. Edelgard could feel the heat leaving her body as she was losing blood. She clenched at her bleeding stomach but not much use. A wyvern took its last breath a few feet away. Was it hers? 

She could not move. Her vision was blurry and darkening, but there was suddenly a familiar presence beside her. 

“Edelgard,” She heard her name, called out with tenderness. Or urgency, she couldn’t tell. It’s Byleth. Her teacher. Just when Edelgard was about to accept her fate, accept that she could go without regret, Byleth came to her side. Maybe there was a little regret. Once upon a time, a school girl’s daydream about what could have been. 

And then, Edelgard was going to die in peace, in the arms of someone she loved. 

And then, a sharp pain on her neck. Barely a sting for a soldier like her. Over too quickly. 

Then, sweet, coppery taste on her lips. Blood.

Edelgard faded to black, and woke as a vampire. In a new era of peace, she was the emperor of everything, and alone.

***

The sun was setting outside the castle. The Emperor’s chamber was embossed with the warm glow of light. Edelgard sat in the shadow and drank her glass of blood.  
The crimson liquid was fresh from a servant’s wrist, probably. She didn’t like to dwell on the details. 

Just that after the war ended, she remembered waking from the worst headache, but there was not a scratch on her body. The imperial healers were stunned by her fast recovery. 

Hubert was the first to realize the condition their professor had left her in. He had a bigger reaction than Edelgard thought he would, but quickly calmed down, back to usual. 

Her inner circle took the news surprisingly well. Better than herself, if she would admit. They were more curious and concerned than afraid, which was great. Dorothea even offered her blood, and Edelgard could just about drink from anything then.

Later, when Edelgard announced that she had emotionally recovered from her transformation (and they almost believed her), they held a council meeting to discuss the future of the empire. Hubert, efficient as always, had secured loyal servants who would donate their blood for “crest research” and paid well enough to keep their mouths shut. 

Vampirism was not a well-known condition across the continent. So it was relatively painless to fool the people.

Edelgard could not fool herself. Byleth lied. Even after Edelgard trusted her with her past and everything, she still lied about such an important part of her life. Not only that, Byleth had transformed her without her permission. It had happened before and Edelgard was sick of it happening again.

Her liar teacher was out there somewhere, living like a wild animal. Disappearance seemed to be her preferred attic. Every time she ran, Edelgard chased after. It’s the one thing that didn’t change. 

Edelgard was going to find her. Once she did, she wanted to ask her the question, once they were face to face. What was on her mind when she did it? Her lips against her skin. The taste of blood. 

It was the closest they’ve ever been, all these years.


	2. Chapter 2

Byleth dug herself out of the haystack when the moon rose. Without a roof over her head, avoiding the sunlight became a pain in the ass. Sunlight could not kill her, but it was an annoyance. She no longer has enough money to pay the innkeeper. Luckily she didn’t need to buy her food. 

Five years was nothing for an immortal being. The years went though like a fever dream. The last battle kept replaying in her head. Every time it did, it stirred up emotions she didn’t know she had. 

She couldn’t help but felt she had lost everything.

The hollowness in her heart drove her to hunt. The fishing towns and shipping ports didn’t have much nightlife, so she was heading for the big city. One bustling with taverns and pubs.

She pretended to drink wine while eyeing for prey. The first time she killed someone was an accident, but it somehow provided an excuse for her moral argument. She had worse control over her impulses, so she only picked those who deserved it, just in case she could not control herself.

There was one man fresh from a bar fight, drunk and cussing and on his way out. Just one look at him, she already knew he was going to taste bad. The smell of blood seeping from his bruises and cuts were tempting. 

She followed him out, watched as he stumbles slowly through the city streets. Entering a dim alleyway, it was almost too perfect. 

She lurched. As she drank, she was becoming intoxicated by the poison in his vein. Her heart sank with every sip, and self-loathing and pity made her want to vomit. She knew every single person she drank from would not compare to *her*. And that she that had blown her chances, once and forever. 

“Hey there, Ashen Demon.”

Alarm bells rang in her head. Byleth let go of the man and took a few steps back, retreated into the darkness. She unconsciously put her hand on the handle of the iron sword at her belt. 

“You’re a really hard woman to find, no?”

If she had a heartbeat, it would have been loud in her ears. Byleth had avoided proper human interaction for a long time. She was afraid she might have thought of them as prey. These days, her control was hairline thin.

Three men appeared at the mouth of the alley, blocking her exit. They were carrying weapons.

Byleth wiped at her blood-stained face, and didn’t clean up better. She might have looked demonic then. 

She could almost imagine Edelgard saying this with a faint smile: “where else do you want to run?”

It’s a high moon and there was not a single soul on the street. Byleth stumbled onto the town center, and found the source of her bad evening.

There was a bounty on her head. Byleth suspected it’s was the work of Edelgard. The brand new poster on the notice board had the royal seal on it. Too bad for her, it didn’t specify dead or alive. The hooligans perhaps thought it meant the Emperor wanted Byleth dead. 

Did she, though?

Exhausted, Byleth found a quiet corner at the back of a bookstore no one visited even during the day. She sat down against the wall, ready to spend the night resting.

“Professor.”

The voice was surprisingly familiar, and that fact startled her. Byleth jerked her head up, and saw the last person she was expected to see. 

Linhardt. The scholar was dressed in casual attire and carrying a satchel of books. 

“You find yourself in an interesting situation, professor,” he said. “Edelgard just want to see you again.”

“I didn’t expect to see you here,” Byleth said, her voice hoarse and felt like sandpaper. 

“Me neither.”

They stared at each other for an awkward moment. 

“Are you going back to Enbarr?" Linhardt asked.

“...” Byleth buried her head in her hands. “What does she...think of this?” She made a gesture but didn’t know what she was gesturing at.

“I don’t know. I haven’t seen her in months.” Linhardt said. He moved to lean his back against the wall, a few feet away. “This is a nice town. It has enough resources for my studies but also quiet enough for sleeping. Until the murders started around these part, then mercenaries are clambering around to search for this bloodthirsty demon. It’s you, isn’t it, professor? Edelgard told us you save her life.”

“She did?”

“Well, not exactly. She said you turned her into a vampire. I never knew you are a vampire.”

“I have been this way for...as long as I remember.”

“And how long is that? A few hundred years? Or only a handful of decades?”

“My memory before the monastery is fuzzy. My days as a mercenary are out of focus and blurred together.”

“Alright,” Linhardt nodded to himself, as if getting the answer he always knew. Then he asked, “This honestly puzzles me, but why do you kill?”

Good question. The front of her robe was still stained with dried blood. It had gotten uncomfortably stiff. If she didn’t have an audience, she would be licking her blood-caked nails until they are clean. But...

“I...am weakened now, compared to five years ago. I think. Sometimes my thoughts are not my own.”

Byleth’s own theory was that turning Edelgard had drained some of her power. She was always hungry. If not for the fact that she just fed on the man, she might even see her former student here as food. 

She shifted slightly, curling up one knee and hugging it. The motion pulled a forgotten wound. It’s at her waist, not deep, but cut by silver. One of those mercenaries must have used a silver dagger. Unlike any other wounds, this one was healing depressingly slow. 

Linhardt watched her from the corner of his eyes. 

“Do you truly want to go back, professor? Edelgard doesn’t like to take no for an answer, but she always likes to follow your wishes,” he said. “I will be writing to her in the morning, what should I say?”

Byleth got up slowly. Now that she was aware of her wound, it pulled every time she moved.

It’s also nice to see that her former student wasn’t afraid of her. He still kept his distance, but he didn’t retreat. 

“Say that...” Byleth pressed a hand there. There was blood, and the wound was a little warm for a cold-blooded creature like her. “I will be meeting her soon.”

**Author's Note:**

> It's been a few years but I've decided to start writing fanfics again.  
> Always wanted to write a serious fic for these two but I saw too many memes lol.  
> Hmu on tumblr: https://glamourscape.tumblr.com  
> Comments really make my day. Thanks.  
> 


End file.
